Finding a vaccine for HIV is one of the most pressing biomedical priorities today. After infection with HIV, enormous virus replication occurs and the decline of this replication coincides with a peak in HIV specific cytotoxic T lymphocytes (CTLs). Antibody responses do not appear until later in the course of the disease. It is thought, therefore, that this CTL response controls viral replication and, thus, it is becoming increasingly clear that a HW vaccine must induce strong CTL responses. In this proposal we will determine the role of CTL in control of viral replication using the SIV-infected rhesus macaque as an animal model for HW-infected humans. We will generate strong CTL responses in the absence of any other SIV-specific immune responses and then challenge the vaccinated animals with SIV. We have already immunized rhesus macaques with DNA and Modified Vaccinia Ankara (MVA) encoding a single relevant CTL epitope and have generated the strongest CTL responses ever seen (1 of 5 CD8 positive fresh PBL specific for the simian AIDS virus). In this proposal we will generate CTL against multiple epitopes in several different SIV proteins. Additionally, we will induce Cm at mucosal sites. This will allow us to test the hypothesis that CTL can ameliorate the course of disease after infection. To carry out these studies we have assembled a team of investigators to fully utilize this animal model. Ashley Haase and Steve Wolinsky will determine the nature of virus replication in situ and the evolution of quasi species, respectively. Yoshi Kawaoka will construct chimeric influenza viruses for induction of CTL at mucosal sites. Chris Miller will infect immunized rhesus macaques intravaginally (IVAG) with a well-defined stock of SIVmac25 1. John Altman will synthesize MHC class I tetramers for CTL quantitation and Deborah Fuller will immunize animals using the gene gun.